Antenna



& E-79,272

R. M. SILLIMAN Aug. 16 1949.

ANTENNA Filed Dec.

INVENTOR. ROBERT M. SILLIMAN BY ATTORNEY Patented Aug. 16, 1949 UNITED OFFICE to the United States of America as repre'sent'd by the Secretary of War The matching" sections of the prior art used to comieet an ahten'fato it transniissi mie have been external to' the anteima structure. Hen-ce, these sections have teen exposed to the dtner of hrkge a'd 'hav thus im`paired' the useful service of the" apratus with which the matching section is assbciated ffort of the prfor art to protect the ma-tchig section by giv'- ih-g it additior-al str'en'gth `byrx'eh'odssuch as reinfoi'ciig it by housing have'provd impracticai, due to* the* resulting bulk of the ap'paratu's; Thi is especia-fi di'sadV-ntgouswhen* the ap'pratus i's'to be'use'd' on aircra-ft whei'e theweightof radio apparatu's is alwys a mejor factor in its'design It is an object of' the preeit inVehti'o to pro Vide' an ahtenha structufe whichis" the same hosihg' with its matching'se cfiion ad which' is `eti'c'l'oseiztby the same ndcel le.

It is' afl'so" ari object of the present' inV-tion to pi ovid'e' an ante'mra; which s'u'rrouds the coaxi'al tra nshissioh' lirie matching setioh which conveys elcti cl'- energy to* it' when' it' is a tran'smittng .amen-na or conveys el'ect'rical energy' from it when the' anteriha' isused to receive ra'diofrquency .sign'ais. v i

It' is another obj'ectof the' pr'esent invention' to provide an 'antenna for operation over a" wide range' o-f radioqfrequencies in= which a matching 'section' is folded into-the interier of the antem-na structure. I I

It is a further object of the present invention to provide anantenna inside of which isa one- Quarter wavelength matching sectionfolded so the outside surface of the ant er nais acon `tinuztion of the inside surface of the outer cond'uctor of the matching section Generallnthis invention comprises a wideb-nd antemia m which a matching section is 'folded iI-to the interier oftH antena structure without iipa'irihg the emci'eric of the atehaj. The ou'tsi desurfac' of the anteffa i's cotiubs with the in'sidesurfa'ce of the oute" conductor' of the matching section; and the' foldih'g of thjs same od't''cto'r` at the top' of the' atenh; structure jbifis it with the" i'-'is'id'e cbductor of the" trns mission" lin V V Other objets; features; and* adtaitge's (si-*this invention wii* suggest theihie tothose' skiiid afrt wi h Become apparent from the foii 'g description" of the' invention taken iri donne with the accomianying drawing which i's' across-s tion'al view' of aii' antenna su'iroii'd iiig'its frthg 'Section af'd' constructe-d in acctrqane with the prii''cipi'esof the preser 't ir' Q E u The' itrm and its'rri'altchirigisection te gert falljdeinatd' on" thedr'aiwir''g' by m; The ctuti configirtio of this' structure' may h're fili'j' appr ciate& s viializihg it as a. figure of reviution aho'ut' the axis ,A-*A The fiteiih; whichconsists' of ai cn'icai section 2 1 a'cylih'dricai section H, is connected to' the matching section which con'sists'of an outer cori ductor !2, inner conductor !5 and the dielectric whi'h* He's betwi theni. 4 H i; energy* c nteyed tothe antenna and that 'ig section by cbnn'ebting n I external b l trfrj'sisibh' ir (not shown) to the The' ri f energy is conv'eyed: to the matching section" by the center conductor' M and utercbdiitor 1 5 of a'* coJXi-l" iine within the eintermstructur The' upper end of the center ritor 14' i's l ectri'clly connected' to the anjtenna l l by screw |6. The center conductor is suoi tedbyin'uiatig'hshing If1 at' the bottom a''fd b flitm hg' ushin 8= at the' top; The edeptr 9 eie ca l ls corriectsthe conductor g` scti on' ohductor !2. In the at the frequency of which the section l2 is a onequarter wavelength is as follows:

Accordingly I claim all such deviations which fall fairly within the spirit and scope of the invention as identified in the hereinafter appended claims.

What is claimed is:

1. A wide band antenna assembly comprising an antenna having a truncated conical portion and a cylindrical portion, a coaxial transmission line located within said portions, a cylindricai matching section comprising a cylindrical conductor concentric with said coaxial line, the outer surface of said line forming the inner conductor of said section, means electrically connecting one ,end of said `cylindrical conductor to the trun- Let us suppose that the matching section is by the design proportions of its length, spacing and dielectric content made one-quarter. wavelength in length at 217 megacycles. At this fre uency the impedance Z presented by the antenna to the matching section !2 is approximately lohms. The matching section l2 has a, characteristic impedance Zo of approximately 40 ohms at about 400 megacycles. If this matching section having an impedance of 40 ohms is used to 'match the 16 ohrns presented by the antenna to it to 100 ohms a standing wave ratio not exceeding two to one results on the transmission line at any frequency from 190 to 650 megacycles. such a wide frequency range coupled with the desirable physical characteristics of this device has made the use of this device particularly advantageous on aircrat. V

The antenna structure hereinbefore described has been designed primarily for use with aircrat and because of its compact design is particularly suitable therefore. The antenna may, of course. be used in other enviromnents. It has also been found that, although desirable, it is not necessary for the matching section to be a quarter wavelength long for any of the frequencies within the band for which the antenna was designed to operate.

From the preceding description it will be clear ;that in accordance with the invention, the antenna structure comprises a hollow, shaped conductive member in spaced relationship adjacent to a conductive surface, this member being reentrant in the region of adjacency to form a cavity therein, the outer shape and size of said member having proportions to provide at the region of adjacency a predetermined antenna impedance characteristic over a chosen band of frequencies. A coaxial line of chosen characteristic impedance and having an inner and an outer conductor, passes through an opening in the conductive surface in the aforementioned region of .adjacency and into the cavity. The outer surface of the outer conductor of the transmission line -is conductively contiguous with the conductive surface and the inner conductor is conductively connected at a point to the inner surface of the cavity. The inner surface of the cavity and the outer surface of the outer conductor which lies within the cavity have chosen dimensions and spacings thereby constituting a line section which is effective to match the impedance of the line to the antenna impedance.

It will be apparent that there may be deviations from the invention as described which still fall fairly within the spirit and scope ofthe invention. u i r v cated end of said conical portion and the other end to the inner conductor of said coaxial line.

2. A wide-band antenna assembly as claimed in claim 1 in which said matching section is a quarter wavelength for one of the frequencies within the Operating band of said antenna.

. 3. A wide band antenna assembly as claimed in claim 1 in which said antenna is enclosed within a housing of insulating material.

4, A wide-bandantenna assembly comprising an antenna having a truncated conical portion and a cylindricalportion, a, conducting ground plane, a coaxial transmission line located within said portions a coaxial matching section comprising a cylindrical conductor concentric with said coaxial line, the outer surface of said line forming the inner conductor of said section means at a first end of said cylindrical conductor electrically connecting theouter conductor of said matching section to the truncated end of said conical portion and the inner conductor of said matching section to said ground plane and means at a second end of said matching section for coupling said matching section to said coaxial line.

5. A wide band `antenna assembly comprising an antenna having a cylindrical portion closed at one end by a conductive base, and a truncated conical portion, the base of said conical portion being electrically connected to the open end of said cylindrical portion, a first tubular conductor disposed within said antenna connecting the truncated end of said conical portion to the base of said cylindrical portion, a second tubular conductor disposed concentrically within said first conductor and insulated from said first conductor and said base, and athird conductor disposed 'concentrically within said second conductor and insulated therefrom, said third conductor making electrical contact with -said conductive base whereby said second and third conductors form a' coaxial line for transferring energy to said antennaandsaid first and second conductors form a coaxial matching section for matching said co- 'axial'line to said antenna.

6. An antenna assembly as claimed in claim 5 wherein the space *between said first and second conductors is filled'with a solid dielectric mate- 'rial to increase the effective electrical length of said matching section.

'7. An antenna assembly as claimed in claim 5 said assembly further comprising means for supporting said first and third conductors from said second conductor whereby said antenna assembly is supported by said second conductor.

. 8. An antenna assembly as claimed in claim 5 said assembly further comprising a conductive ground plane, means for supporting said second conductor from said ground plane, and means for supporting said first and said third conductor from said second conductor whereby said antenna is supported by a predetermined distance above said conductive ground plane.

9. .An antenna structure comprising a hollow shaped conductive member supported in spaced relationship adjacent to a conductive surface, said member being re-entrant in the region of adjacency to form a cavity therein, the outer shape and size of said member having proportons to provide at said region of adjacency a predetermined antenna impedance characteristic over a chosen band of frequencies, a coaxial line of chosen impedance having an inner and an outer conductor, said line passing through an opening in said surface in the said region of adjacency and into said cavity, the outer surface of said outer conductor being conductively contiguous with said surface and said inner conductor being conductively connected at a point to the inner surface of said cavity, said inner surface of said cavity and the outer surface of said outer conductor which lies within said cavity having chosen dimensions and spacings to constitute a line section which effectively matches the impedance of said line with the impedance of said antenna over said chosen band of frequencies.

10. An antenna structure comprising a hollow shaped conductive member supported in spaced relationship adjacent to a conductive surface, said member being re-entrant in the region of adjacency to form a cavity therein, the outer shape and size of said member having proportions to provide at said region of adjacency a predetermined antenna impedance characteristic over a chosen band of frequencies, a coaxial line of chosen impedance having an inner and an outer conductor, said line passing through an opening in said surface in the said region of adjacency and into said cavity, the outer surface of said outer conductor being conductively contiguous with said surface and said inner conductor being conductively connected at a point to the inner surface of said cavity, a dielectric support for said member filling the space between said inner surface of said cavity and the outer surface of said 4 outer conductor which lies within said cavity, said surfaces having chosen dimensions and spacings to constitute a line section which effectively matches the impedance of said line and the impedance of said antenna over a chosen band of frequencies.

11. An antenna structure comprising a hollow shaped conductive member supported in spaced relationship adjacent to a conductve surface, said member being re-entrant in the region of adjacency to form a cavity therein, the outer shape and size of said member having proportions to provide at said region of adjacency a predetermined antenna impedance characteristic over a chosen band of frequencies, a coaXial line of chosen impedance having an inner and an outer conductor, said line passing through an opening in said surface in the said region of adjacency and into said cavity, the outer surface of said outer conductor being conductively contiguous with said surface and said inner conductor being conductively connected at a point to the inner surface of said cavity, dielectric material filling the space within said cavity, said inner surface of said cavity and the outer surface of said outer conductor which lies within said cavity having chosen dimensions and spacings to constitute a line section which effectively matches the impedance of said line and the impedance of said antenna over a chosen band of frequencies and more clo sely matches at a chosen frequency at the lower end of said band.

12. An antenna structure comprising a hollow shaped oonductive member supported in spaced relationship adjacent to a conductive surface, said member being re-entrant in the region of adjacency to form a cavity therein, the outer shape and size of said member having proportions to provide at said region of adjacency a predetermined antenna impedance characteristic over a chosen band of frequencies, a coaxial line of chosen impedance having an inner and an outer conductor, said line passing through an opening in said surface in the said region of adjacency and into said cavity, the outer surface of said outer conductor being conductively contiguous with said surface and said inner conductor being connected at a point to the inner surface of said cavity, dielectric material filling the space within said cavity, said inner surface of said cavity and the outer surface of said outer conductor which lies within said cavity having chosen dimensions and spacings to constitute a line section of a quarter wave length at a chosen frequency thereby to match the impedance of said line and the impedance of said antenna over a chosen band of frequencies.

ROBERT M. SILLIMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,184,72-9 Bailey Dec. 26, 1939 2,210,066 Cork Aug. 6, 1940 2,251,997 Goldmann Aug. 12, 1941 2,275,646 Peterson Mar. 10, 1942 2,287,220 Alford June 23, 1942 2,323,641 Bailey July 6, 1943 23401501 Atwood June 4, 1944 FOREIGN PATENTS Number Country Date 260,005 Great Britain Mar. 24, 1927 414296 Great Britain Aug. 2, 1934 878,564 France Jan. 25, 1943 

